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Faster surface hardening technique saves energy

12 August 2015

Surface hardening such as pack-boriding is both time-consuming and energy-intensive. A US team has developed a process for ultra-fast boriding that saves time, money and energy.

A newly patented technology by Ali Erdemir and his team at the US Department of Energy’s Argonne National Laboratory could greatly extend the lifetime of mechanical parts. In a departure from the conventional boriding technique, which is both time-consuming and energy-intensive, Erdemir and his team have come up with a process for ultra-fast boriding that saves time, money and energy, and even alleviates environmental concerns.

In three years, Erdemir and his team took an abstract concept and turned it into an industrial-scale furnace that can deposit a boride layer 100 micrometres thick in half an hour. To achieve this same thickness, pack-boriding would need approximately ten hours.

Now, just a few years after completing the process, Erdemir’s group has been awarded a utility patent covering the ultra-fast nature of the technology, the range of materials that can be treated and several specific steps in the process of ultra-fast boriding.

Where pack-boriding involves baking parts in a complex mix of powders at temperatures close to 1,000°C, often for ten hours or more, the ultra-fast method uses a battery-like design to channel reactive boron into metal surfaces. Like a battery, the furnace relies on the attraction between positive and negative charges to get boron flowing swiftly toward its destination.

Because boron is supplied so quickly, the layers produced by ultra-fast boriding are more uniform and dense than the results of conventional pack-boriding. Ultra-fast boriding also creates tougher layers than any existing option for surface hardening, including the use of carbon or nitrogen in place of boron. A thicker protective layer is unlikely to crack or come loose, so it increases the lifetime of treated metal parts.

According to Erdemir, the heating process alone makes pack-boriding extremely energy-intensive. Ultra-fast boriding can do a better job while using 80 to 90 percent less energy. And while the powder mix-based traditional boriding releases carbon dioxide and other hazardous emissions, the ultra-fast alternative releases almost none, he said.

The scientists are now collaborating with a private industry partner to get a large-scale furnace into commercial operation.